ext3_extents.h revision f926a7006de647132fff634b9fd9c1fa8f41abd4 
1/*
2 * Copyright (c) 2003,2004 Cluster File Systems, Inc, info@clusterfs.com
3 * Written by Alex Tomas <alex@clusterfs.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public Licens
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
17 */
18
19#ifndef _LINUX_EXT3_EXTENTS
20#define _LINUX_EXT3_EXTENTS
21
22/*
23 * ext3_inode has i_block array (total 60 bytes)
24 * first 4 bytes are used to store:
25 *  - tree depth (0 mean there is no tree yet. all extents in the inode)
26 *  - number of alive extents in the inode
27 */
28
29/*
30 * this is extent on-disk structure
31 * it's used at the bottom of the tree
32 */
33struct ext3_extent {
34	__u32	ee_block;	/* first logical block extent covers */
35	__u16	ee_len;		/* number of blocks covered by extent */
36	__u16	ee_start_hi;	/* high 16 bits of physical block */
37	__u32	ee_start;	/* low 32 bigs of physical block */
38};
39
40/*
41 * this is index on-disk structure
42 * it's used at all the levels, but the bottom
43 */
44struct ext3_extent_idx {
45	__u32	ei_block;	/* index covers logical blocks from 'block' */
46	__u32	ei_leaf;	/* pointer to the physical block of the next *
47				 * level. leaf or next index could bet here */
48	__u16	ei_leaf_hi;	/* high 16 bits of physical block */
49	__u16	ei_unused;
50};
51
52/*
53 * each block (leaves and indexes), even inode-stored has header
54 */
55struct ext3_extent_header {
56	__u16	eh_magic;	/* probably will support different formats */
57	__u16	eh_entries;	/* number of valid entries */
58	__u16	eh_max;		/* capacity of store in entries */
59	__u16	eh_depth;	/* has tree real underlaying blocks? */
60	__u32	eh_generation;	/* generation of the tree */
61};
62
63#define EXT3_EXT_MAGIC		0xf30a
64
65/*
66 * array of ext3_ext_path contains path to some extent
67 * creation/lookup routines use it for traversal/splitting/etc
68 * truncate uses it to simulate recursive walking
69 */
70struct ext3_ext_path {
71	__u32				p_block;
72	__u16				p_depth;
73	struct ext3_extent		*p_ext;
74	struct ext3_extent_idx		*p_idx;
75	struct ext3_extent_header	*p_hdr;
76	struct buffer_head		*p_bh;
77};
78
79/*
80 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
81 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
82 * MSB of ee_len field in the extent datastructure to signify if this
83 * particular extent is an initialized extent or an uninitialized (i.e.
84 * preallocated).
85 * EXT_UNINIT_MAX_LEN is the maximum number of blocks we can have in an
86 * uninitialized extent.
87 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
88 * uninitialized one. In other words, if MSB of ee_len is set, it is an
89 * uninitialized extent with only one special scenario when ee_len = 0x8000.
90 * In this case we can not have an uninitialized extent of zero length and
91 * thus we make it as a special case of initialized extent with 0x8000 length.
92 * This way we get better extent-to-group alignment for initialized extents.
93 * Hence, the maximum number of blocks we can have in an *initialized*
94 * extent is 2^15 (32768) and in an *uninitialized* extent is 2^15-1 (32767).
95 */
96#define EXT_INIT_MAX_LEN	(1UL << 15)
97#define EXT_UNINIT_MAX_LEN	(EXT_INIT_MAX_LEN - 1)
98
99#define EXT_FIRST_EXTENT(__hdr__) \
100	((struct ext3_extent *) (((char *) (__hdr__)) +		\
101				 sizeof(struct ext3_extent_header)))
102#define EXT_FIRST_INDEX(__hdr__) \
103	((struct ext3_extent_idx *) (((char *) (__hdr__)) +	\
104				     sizeof(struct ext3_extent_header)))
105#define EXT_HAS_FREE_INDEX(__path__) \
106	((__path__)->p_hdr->eh_entries < (__path__)->p_hdr->eh_max)
107#define EXT_LAST_EXTENT(__hdr__) \
108	(EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_entries - 1)
109#define EXT_LAST_INDEX(__hdr__) \
110	(EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_entries - 1)
111#define EXT_MAX_EXTENT(__hdr__) \
112	(EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->eh_max - 1)
113#define EXT_MAX_INDEX(__hdr__) \
114	(EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->eh_max - 1)
115
116#endif /* _LINUX_EXT3_EXTENTS */
117
118